This invention relates generally to ejectors, and, more particularly, to an ejector motive nozzle that may be used in pumping, compression, or mixing applications.
At least some known ejectors mix two flow streams, a high-pressure (“motive”) stream and a low-pressure (“suction”) stream, so as to produce a discharge flow with pressure intermediate to or lower than the two input flows. The ejector motive nozzle facilitates this mixing process by accelerating the high-pressure motive flow, thereby creating a high speed jet that is channeled through a mixing tube or chamber to entrain the low pressure suction flow. The two mixed flows are then discharged, typically through a diffuser.
Some known ejectors use a motive nozzle that is surrounded by a casing and includes a nozzle tip having a round or rectangular cross-section oriented about an axis of the ejector. At least some known nozzles may create a motive jet that oscillates in a bending mode, producing coherent flow disturbances such as partial ring vortex structures at an edge of the jet. When these coherent flow disturbances strike a downstream wall of the casing, reflected acoustic waves may be produced and feedback towards the nozzle. The feedback waves may reinforce the jet bending oscillations and result in a fluid dynamic resonance that may produce damaging structural loads and/or high noise levels within the ejector. Over time, fluctuating loads produced by this fluid dynamic resonance may decrease the lifespan of the ejector or other hardware, add to maintenance costs, and/or create objectionable levels of environmental noise.